From 3800c0df910c83e987184d541b868168fc2b5bec Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Fri, 8 May 2009 21:08:08 +0000
Subject: svn merge -r114679:114681
 svn+ssh://svn.lindenlab.com/svn/linden/branches/event-system/event-system-7
 svn+ssh://svn.lindenlab.com/svn/linden/branches/event-system/event-system-8

---
 indra/llcommon/lldependencies.cpp | 86 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 indra/llcommon/lldependencies.cpp

(limited to 'indra/llcommon/lldependencies.cpp')

diff --git a/indra/llcommon/lldependencies.cpp b/indra/llcommon/lldependencies.cpp
new file mode 100644
index 0000000000..ffb5cfbdaa
--- /dev/null
+++ b/indra/llcommon/lldependencies.cpp
@@ -0,0 +1,86 @@
+/**
+ * @file   lldependencies.cpp
+ * @author Nat Goodspeed
+ * @date   2008-09-17
+ * @brief  Implementation for lldependencies.
+ * 
+ * $LicenseInfo:firstyear=2008&license=viewergpl$
+ * Copyright (c) 2008, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+// Precompiled header
+#include "linden_common.h"
+// associated header
+#include "lldependencies.h"
+// STL headers
+#include <map>
+#include <sstream>
+// std headers
+// external library headers
+#include <boost/graph/graph_traits.hpp>  // for boost::graph_traits
+#include <boost/graph/adjacency_list.hpp>
+#include <boost/graph/topological_sort.hpp>
+#include <boost/graph/exception.hpp>
+// other Linden headers
+
+LLDependenciesBase::VertexList LLDependenciesBase::topo_sort(int vertices, const EdgeList& edges) const
+{
+    // Construct a Boost Graph Library graph according to the constraints
+    // we've collected. It seems as though we ought to be able to capture
+    // the uniqueness of vertex keys using a setS of vertices with a
+    // string property -- but I don't yet understand adjacency_list well
+    // enough to get there. All the examples I've seen so far use integers
+    // for vertices.
+    // Define the Graph type. Use a vector for vertices so we can use the
+    // default topological_sort vertex lookup by int index. Use a set for
+    // edges because the same dependency may be stated twice: Node "a" may
+    // specify that it must precede "b", while "b" may also state that it
+    // must follow "a".
+    typedef boost::adjacency_list<boost::setS, boost::vecS, boost::directedS,
+                                  boost::no_property> Graph;
+    // Instantiate the graph. Without vertex properties, we need say no
+    // more about vertices than the total number.
+    Graph g(edges.begin(), edges.end(), vertices);
+    // topo sort
+    typedef boost::graph_traits<Graph>::vertex_descriptor VertexDesc;
+    typedef std::vector<VertexDesc> SortedList;
+    SortedList sorted;
+    // note that it throws not_a_dag if it finds a cycle
+    try
+    {
+        boost::topological_sort(g, std::back_inserter(sorted));
+    }
+    catch (const boost::not_a_dag& e)
+    {
+        // translate to the exception we define
+        std::ostringstream out;
+        out << "LLDependencies cycle: " << e.what() << '\n';
+        // Omit independent nodes: display only those that might contribute to
+        // the cycle.
+        describe(out, false);
+        throw Cycle(out.str());
+    }
+    // A peculiarity of boost::topological_sort() is that it emits results in
+    // REVERSE topological order: to get the result you want, you must
+    // traverse the SortedList using reverse iterators.
+    return VertexList(sorted.rbegin(), sorted.rend());
+}
+
+std::ostream& LLDependenciesBase::describe(std::ostream& out, bool full) const
+{
+    // Should never encounter this base-class implementation; may mean that
+    // the KEY type doesn't have a suitable ostream operator<<().
+    out << "<no description available>";
+    return out;
+}
+
+std::string LLDependenciesBase::describe(bool full) const
+{
+    // Just use the ostream-based describe() on a std::ostringstream. The
+    // implementation is here mostly so that we can avoid #include <sstream>
+    // in the header file.
+    std::ostringstream out;
+    describe(out, full);
+    return out.str();
+}
-- 
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